1. Field of the Invention
The present invention relates to an air cleaner which is suited for use in the suction system of a small air-cooled two-stroke gasoline engine of a portable working machine. More particularly, the invention relates to an air cleaner provided with a novel bellows-like air cleaning filter.
2. The Prior Art
A typical example of the conventional air cleaner is shown in FIGS. 15 and 16. This air cleaner 50 is intended to be employed in the suction system of a small air-cooled two-stroke gasoline engine, of a portable working machine for instance, and is provided with an air cleaning filter 52 made of an air-permeable filter paper folded into a bellows-like shape, in order to increase the filtering area thereof, and formed into a cylindrical shape as shown in FIG. 15. The air cleaner 50 further comprises an inner cylindrical member 56 disposed inside of the air cleaning filter 52, which functions as a shape-retaining member to maintain the air cleaning filter 52 cylindrical in shape. The cylindrical member 56 is made of punched metal having a large number of vent holes 56a. An annular end cap 59 is attached to each of the upper and lower end portions of the air cleaning filter 52 and the inner cylindrical body 56.
Since the bellows-like air cleaning filter 52 is formed of a filter paper in the conventional air cleaner 50 as described above, it is not only impossible to wash the air cleaning filter 52 with water or gasoline, but it is also difficult to clean the filter 52 by use of compressed air. This presents a problem in the maintenance of the air cleaning filter 52. Furthermore, since an air cleaning filter 52 that is made of a bellows-like filter paper is not strong enough to retain its cylindrical shape by itself, some kind of shape-retaining member (e.g. the inner cylindrical member 56 made as a punched metal member) is required to retain the cylindrical shape of the filter 52, thus increasing manufacturing and assembly costs.